In the food processing, in particular, the beverage industry, the cleaning, filling and labeling, etc. of bottles are carried out automatically. The bottles are moved from operation station to operation station on belt conveyors. In order to keep the conveyor chains cleaned and provide lubrication, aqueous based lubricants are used. Generally, these lubricants are manufactured as concentrates and are diluted, for example, in 1 to 100, or 1 to 1000 with water at the point of use. Some of these lubricants are soap-based as is disclosed by Aepli et al., U.S. Pat. No. 3,860,521. A disadvantage of these lubricating agents is that soaps are sensitive to water hardness. Sequestering agents such as ethylenediamine tetraacetic acid (EDTA) are added to partially mask the hardness. Hardness, usually associated with magnesium and calcium ions, tend to reduce the effectiveness of the lubricating agent. These hardness ions tend to precipitate salts leading to lubricating problems.
Synthetic amine-based lubricating agents are also known. While these amine-based lubricating agents do not have the problems associated with the soap-based lubricants, they tend to react with ions such as carbonates and sulfates which are present in water, thus reducing the lubricating effect. Furthermore, some amines together with other ingredients and constituents such as alcohol that are present in lubricants can have a deleterious effect on thermoplastics such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polysulfone and polycarbonate. At the present, thermoplastics are widely used in the beverage industry due to their availability, inexpensive nature, and their unique plastic properties.
Many different formulations of lubricants have been disclosed in the past. The aforementioned Aepli et al. U.S. Pat. No. 3,860,521 disclose an aqueous lubricating concentrate for lubricating continuously moving conveyor system. This concentrate contains a fatty acid soap and a surfactant. The improvement comprises the addition to the lubricating composition of monostearyl acid phosphate.
Anderson et al., U.S. Pat. No. 4,521,321 disclose a lubricant concentrate comprising a partially neutralized monophosphate ester having a saturated or partially unsaturated linear alkyl group of C.sub.12 to C.sub.20, and the use of synergistic ingredients such as a long chain alcohol and fatty derived amine oxide to improve the properties of the lubricant compositions.
Stanton, U.S. Pat. No. 4,604,220 discloses a conveyor cleaner-lubricant concentrate derived from a concentrate of C.sub.12 to C.sub.18 alpha olefin sulfonate, and water or a water soluble solvent. The sulfonate concentrate can be directly diluted with water to form a cleaner lubricant or it can be directly added to soap lubricants.
Jansen, U.S. Pat. No. 4,839,067 discloses a process for the maintenance of chain type bottle conveyor belts in beverage plant wherein the bottle conveyor belts are lubricated with lubricating agents with a base of neutralized primary fatty amines and are cleaned with cationic cleaning agents or organic acids.
Weber et al., U.S. Pat. No. 5,062,978 disclose an aqueous lubricant solution consisting essentially of fatty alkyl amines which contains a saturated or unsaturated, branched or linear alkyl group having 8 to 22 carbon atoms.
It has long been known in the industry by the people skilled in the art that lubricants lead to a phenomenon which is commonly called "stress cracking." That is particularly prevalent in PET, polysulfone, polycarbonate containers and the like. A number of conventional aqueous based lubricants which contain alcohol and/or amines tend to promote stress cracking. Wider et al., U.S. Pat. No. 5,009,801 allegedly disclose a method for reducing stress cracking in polyalkylene terephthalate articles by using a stress cracking inhibitor which comprises a hydrophilic-substituted aromatic hydrocarbon having either an alkyl or an aryl side chain. Rossio et al., U.S. Pat. No. 5,073,280 allegedly disclose an aqueous fatty acid based lubricant comprising a stress crack inhibitor which is an alkylamine with at least 6 carbon atoms.
Alkylpolyglycosides, or alkyl substituted polyglycoside, are naturally derived nonionic surfactants. Generally, they are mild, moderately foaming, and highly soluble. An alkylpolyglycoside is a surfactant that contains a carbohydrate hydrophile with multiple hydroxyl groups, and are soluble in high levels of acids, bases, and electrolytes. Typically, they are non-gelling and insensitive to temperature change. Their unique physical, chemical and ecological properties make alkylpolyglycosides very attractive for formulating household and industrial cleaning applications such as hand and dishwashing and laundry detergents.
Cook et al., U.S. Pat. No. 4,536,318 discuss a foaming composition containing an alkyl polysaccharide surfactant and a co-surfactant mixture consisting essentially on an alkyl benzene sulfonate, wherein the saccharide moiety is derived from a reducing saccharide containing from 5 to 6 carbon atoms such as glucose, galactose, grucosyl, or grucosyl residue and the hydrophobic group is selected from the group consisting of alkyl, alkyl phenyl, hydroxyl alkyl phenyl or hydroxy alkyl group.
Roth et al., U.S. Pat. No. 4,834,903 describe the use of alkaline oxide adducts of relatively low degree of polymerization long chain glycoside composition composed of long chain monoglycoside species wherein the hydrophobic group contains 6 to 20 carbon atoms and the reducing saccharide contains 5 to 6 carbon atoms.
Vogt et al., U.S. Pat. No. 4,919,845 discuss a detergent composition containing nonionic surfactants including alkylglycosides and alkylpolyglycosides wherein the alkyl group contains 8 to 18 and preferably 10 to 16 carbon atoms.
McDaniel, U.S. Pat. No. 5,001,114 relates the use of new alkyl mono and polyglycoside phosphate esters and anionic derivatives thereof wherein the glycosyl moiety is selected from the group consisting of fructose, lactose, mannose, galactose, talose, gulose, allose, altrose, idose, arabinose, xylose, lyxose, and ribose, and the hydrophobic group is an aliphatic or aromatic hydrocarbon group.
McCurry et al., U.S. Pat. No. 5,003,057 disclose a process for the preparation of glycosides. The process comprises reacting in the presence of an acid catalyst an alcohol with a source of saccharide moiety, wherein the acid catalyst comprises a strong hydrophobic organic acid.
Jordan et al., U.S. Pat. No. 5,076,593 disclose a mild skin cleansing bar composition comprising alkylglycosides.
Fabry et al., U.S. Pat. No. 5,014,585 describe a detergent mixture containing at least one alkylglycoside having an aliphatic radical containing at least 8 carbon atoms, preferably a primary alcohol radical, and a glucose unit derived from a reducing saccharide containing 5 or 6 carbon atoms.
None of the aforementioned patents discloses the use of alkylpolyglycosides in aqueous lubricant solutions that prevents or reduces stress cracking in thermoplastic containers. There is one reference, van de Brom et al., European Patent Application No. 90203211.9, that describes the application of alkylpolyglycosides in a composition of plastics compatible detergents and rinse aids.
However, we are not aware of any patent or publication that teaches the use of alkylpolyglycosides in a conveyor belt lubricating composition.
Typically, conveyor lubricants that are compatible with PET, PBT or polybutylene terephthalate, polycarbonate and polysulfone and the like are not very effective as detergents or cleaning agents. Preferably a lubricant would contain ingredients that would provide detergency or cleaning properties so that the lubricants can also promote cleanliness. There is a need for lubricants having detergency property that are compatible with thermoplastics such as PET, PBT, polysulfone, polycarbonate and the like. Furthermore, because of the present concern for environmental compatibility and toxicity of chemicals used in food processing industry, there is a need for lubricants that contain ingredients that are biodegradable, nontoxic and derived from renewable resources.